Functional particulate matter may be incorporated into a fibrous structure for a variety of reasons. For example, chemical defense fabrics for military personnel may contain vapor sorptive particles such as activated carbon. These fabrics typically are designed to remove poisonous gases from the air. Filter media or filters may include sorptive particles for selectively removing certain components of a liquid or gas passing through the filter. Abrasive particles may be used to create an abrasive fabric. Functional particulate matter may also be used to release an active or desirable agent into a fluid stream, and may be chemically or catalytically reactive with a fluid stream constituent.
Fibrous structures containing solid particulate matter are known, as illustrated by U.S. Pat. Nos. 3,971,373 to Braun, 4,429,001 to Kolpin et al, 4,795,668 to Krueger et al, 4,868,032 to Eian et al, 5,082,720 to Hayes, 5,077,116 to Lefkowitz, 4,872,220 to Haruvy et al, 4,904,343 to Giglia et al, and 3,998,988 to Shimomai et al, and as further illustrated by European Patent Application Nos. 275,047, published on Jul. 20, 1988, and 93-208373. Braun describes physically forming a three dimensional arrangement of particles in a melt blown web. Kolpin et al describe sorbent particulate physically held in place.
Krueger et al teach molding a shaped filtration structure from a bicomponent fiber-blown web. The nonwoven web is preferably formed from microfibers, and may include particles bonded to the fibers, to provide enhanced mechanical filtration. The filtration structure may include other layers. Eian et al describe a melt blown web containing a three dimensional arrangement of particles. The web is formed from unicomponent fiber and includes transversely extending reinforcing, bicomponent fiber. Eian et al teach the advantage of a crimping action during melt bonding. Hayes avoids bicomponent fibers having latent crimpability, in forming the abrasive webs thereof.
Lefkowitz describes a forming fabric to which may be adhered a non-woven web, or which may include particles bridging across fabric interstices, for fines retention. European 93-208,373 describes a bicomponent fiber web containing active carbon particles adhered to the fiber.
One problem that has been encountered is that garments containing particulate matter typically do not last for a suitable period of time. Washing and other stresses can result in delamination of the fabric layers, loss of particulate matter, and other deterioration. Adherence of particulate matter to the surfaces of a web may interfere with bonding between layers. Also, particles adhered to web surfaces, are subject to abrasive removal.
Accordingly, despite the foregoing advances, an improved fibrous structure containing a three dimensional arrangement of functional particulate, is needed. It is desirable for particulate to be immobilized without deleterious reduction in particulate surface area. It is desirable for the web structure to be capable of high loading with particulate. It is desirable for the particulate to be located so as not to interfere with bonding between layers or be subject to abrasive loss. Furthermore, it is desirable for the size of void spaces to be controllable.